Method and apparatus for cold rolling strip metal



Nov. 21, 1939 L. IVERSEN 2.1 80,635

METHOD AND APPARATUS FOR COLD ROLLING STRIP METAL Filed July 15, 1935 3Sheets-Sheet 1 INVENTOR Nov. 21, 1939. L. IVERSEN 2,180,

' METHOD AND APPARATUS FOR com) ROLLING STRIP METAL Filed July 15, 19353 Sheets-Sheet 2 Patented Nov. 21, 19:39

METHOD PATENT OFFICE AND APPARATUS FOR COLD ROLL- ING STRIP METAL LorenzIversen, Pittsburgh, Pa., assignor to Mesta Machine Company, Pittsburgh,Pa., a corporation of Pennsylvama Application July 15, 1935, Serial No.31,432

13 Claims.

This invention relates to, the cold rolling of strip metal in acontinuousjmill; that is to say, in a mill consisting of a series ofstands adapted to work successively on the metal, different portions ofthe strip being acted upon by two or more stands of the mill at the sametime. It is now well recognized that in cold rolling the compressiveforce of the rolls and tension on the strip are both important factorsafiecting the reduction. With increasingly close gauge tolerances itbecomes necessary to effect a close control of these factors. It hasheretofore been proposed (Bedell Patent 1,964,241, dated June 26, 1934),to deflect the strip from a straight-line path as it travels between'successivestands of a tandem mill so as to maintain a substantiallyconstant tension on the strip. It has also been proposed to maintain asubstantially unvarying tension by using electric driving motors for themill stands,

which motors have suitable characteristics, as,

for example, a drooping power curve. The difllculty with these priorsystems has been that they presuppose a uniform and unvarying quality ofstrip. As a matter of fact, however, the hot rolled strip which is usedas a starting material in a cold rolling operation may for a variety ofreasons be non-uniform. For example,"it may-have hard spots which offerundue resistance to reduction, and unless special treatment is accordedto these. hard spots there will inevitably be variations more-or lessserious in the gauge of the strip. The systems heretofore employed havenot been adequate to meet situations such as that just described,. and afurther difflculty attendant 35 upon electric motor control orregulation is that the inertia of the moving parts is such as todestroyany possibility of instantaneous response to a changed condition.In consequence systems of that sort have not only failed to overcome thedifflculties but hafle induced additional gauge variations by reasonofthe hunting which occurs.

I have found that superior resultsmay be obtained by deflecting thestrip out of a straightline path between stands and subjecting it to avarying tension, the amount of tension being automatically adjusted inaccordance with the characteristics of successive portions of the stripas it travels through the mill. Preferably the degree of pressurevariation is lessened in the later stages 0 of reduction. At this timethe differences in hardness between successive portions of strip willhave been lessened in some degree by reason of the eifect of cold work.

I so arrange the mill and its associated parts 55 that a relativelyshort length of strip is subjected to deflection at any time. This notonly makes for accuracy of tension effect but, what is more important,limits the effect of the varied tension to that portion of the stripwhich, because of its special characteristics, requiresan adjustment ofthe reducing forces. Suppose that there be a hard spot in a strip, thehard portion having a length, say, of five feet. It isnecessary toincrease the tensile force which is applied to the strip .in order toreduce this hard spotin the same amount as the adjacent portions of thestrip. Obviously the increased tension should be applied for only arelatively limited period of time as otherwise its effect will beapplied to the portions of the strip adjacent the hard spot and willreduce them unduly. I therefore place the roll stands relatively closetogethernot more than twelve work roll diameters apartandpreferably'limit the span overwhich the advancing strip is deflected tonot more than six work roll diameters.

In the accompanyingdrawings illustrating a present preferred embodimentof the invention,

Figure l is a diagrammatic view of a continuous mill employing theinvention;

Figure 2 is a longitudinal section to enlarged scale of a portion of oneof the mill stands, and

the associated tensioning mechanism;

Figure 3 isa section on the line IIIlII of Figure 2; and Figures 4 to 7inclusive are diagrammatic views showing the various tension cifectswhich may be secured by suitable adjustment of the tension device.

The mill shown in Figure 1 comprises a series of stands 2, 3, 4 and 5adapted to successively engage and cold roll steel strip fed from a coilholder 6. Each of the stands is shown as being of the well-known 4-hightype having working rolls I and backing rolls 8 of larger diameter. Theworking rolls are driven through gear reductions 9 by strip passes outof the last stand, it is coiled on a reel I2 driven by a motor l3through gearing 13a.

7 In the mill shown the working rolls are 18 motors ID of the constantspeed type. After them spaced approxi- The tensioning rollers it areactuated and controlled by mechanism illustrated in detail in Figures 2and 3. The same structure is employed between each two successive millstands and a de- 5 scription of one will suffice for all. However, ashereinafter explaineddifferent adjustments are employed in differentcases.

The tension roller I6 is mounted in a lever l1 pivoted on a cross shaft3 mounted in the housing 10 IQ of the mill stand. The lever Ill has anarm 20 which is connected by a link 2| to a lever 22. The lever 22 isprovided with three holes A, B and C arranged to accommodate a pin 23which makes the pivotal connection between the link 2| and the lever 22.By placing the pin in different holes different effective lever linkscan be obtained. The lever 22 rocks on'a fulcrum pin 24 mounted on abase 25. The fulcrum pin is movable to any one of a variety ofpositions, four of which are indicated at W, X, Y and Z. The

mounting of the fulcrum pin is best shown in Figure 3. It is formed withroller portions 26 run- I ning on tracks 2! formed on the base andcarries pinions 28 meshing with racks 29 fixed in 25 the base. Rotationof the fulcrum pin causes it to move along the tracks 21, the rack andpinion construction insuring positiveness of movement. Rotation of thefulcrum pin is effected by an adiusting lever 30 having a latchconnection 3| 30 with an extension 32 of the fulcrum pin. A

thumb button 33 permits of engaging or disengaging the latch connection,as desired, so that the operating lever 30 can be conveniently. used.Operation of the main lever 22 does not exert any 5 force tending todisplace the fulcrum pin 28 from any adjusted position, and anyinconsequential forces which may tend to move it are effectuallyresisted by the mere weight of the operating lever 30 which, when thefulcrum pin has been moved to the desired adjusted position, is allowedto rest against a cross bar 38. The tensioning roller I6 is urgedupwardly through the mechanism just described by means of a weight Wattached to a plunger 35 and oper- The plunger 35 is carried in abearing sleeve 31 line between successive stands, and'have alsoindicated more or less arbitrarily top, bottom and middle positionswhich the roller l6 may take.

Figures 4 to 6 inclusive show the tension exerted on the strip fordifferent settings of .the several elements above enumerated. Figure 4,for example, shows the amount of tension in different positions of theroller it with the fulcrum pin located at W. There are three curves inthis figure lettered A, B andC corresponding to positioning of the pin23 in each of the holes A, B

and C.

In the earlier stages of reduction the apparatus will be so adjusted asto exert considerable force, lesser forces being employed as thereduction proceeds. The total magnitude of the force, as well as theamount of variation'therein for any given movement of the roller it maybe ating in a cylinder 36 connected to the base 25.

readily fixed by the adjustments heretofore ric scribed.

In operation, if, say, the stand 2 fails to reduce a given portion ofthe strip in the same amount as adjacentportions, as, for example, if ahard spot is encountered, there is a corresponding decrease inelongation and as the hard spot travels over the span between the standin which it was just rolled and the succeeding stand, the roller It willbe deflected downwardly, thus increasing the tension on the strip andcorrespondingly increasing the amount of reduction effected on the hardspot in the succeeding stand because of the increased back tension whichis applied. Similarly, if an undue reduction is effected in a standthere is a corresponding increase in elongation with consequent decreasein the tension.

The apparatus functions promptly whenever a condition such as this isencountered, and its effect is substantially limited to that portion ofthe strip which requires correction. Even though the effect be reflectedin some small measure on portions of the strip at either side of theiard or soft spot, nevertheless the desired gauge is more closelyapproximated throughout the strip, and as successive stands andsuccessive tension devices operate on the strip all irregularities areminimized or eliminated. This is especially so if the tension variationsare reduced as the strip progresses through the mill.

An important feature of my invention is that thezcontrol is effectedindependently of the drive. The stands are driven, each at constantspeed, and the necessity for complex electrical controls supposedlyfunctioning to correct variations in the strip may be dispensed with.

I have illustrated and described a present preferred embodiment of theinvention, but it will be understood that the same is not limitedthereto but may be otherwise embodied or practiced within the scope ofthe following claims.

I claim:

1. In the method of cold rolling strip metal in a tandem mill having aplurality of driven stands, the steps consisting in driving the standseach at constant speed, subjecting the strip to successive coldreductions in the several stands, maintaining the strip under tensionbetween two successive stands, and varying the tension between suchstands independently of the driving of the stands.

2. In the method of cold rolling strip metal in a tandem mill having aplurality of -driven stands, the steps consisting in driving the severalstands each at constant speed, subjecting the strip to successive coldreductions in the stands, main- ,taining the strip under tension betweenstands,

and varying such tension.

3. In the method of cold rolling strip metal in a tandem mill having aplurality of driven stands, the steps consisting in driving the standseach at constant speed-subjecting the strip to successive coldreductions in the several stands, maintaining the strip under a varyingtension between successive stands, to compensate for irregularities inthe strip, the amount of variation being less between later stands ofthe mill than between preceding stands. a

4. Apparatus for the cold rolling of metal strip 1 comprising spacedsubstantially constant speed roll stands adapted for the continuousrolling of the strip, means between the stands for deflecting the stripfrom a straight-line path, and means biasing the deflecting means and'efiective for imposing a tension on the strip which decreases withincreasing departure of the strip from a straight-line path betweenstands.

6. Apparatus for the cold rolling of metal strip comprising a pair ofmills adapted for the continuous rolling of the strip, means for drivingthe mills each at constant speed, and means arranged to engage the stripbetween two suchmills and subject it to a varying tension.

7. Apparatusfor the cold rolling of metal strip comprising a pair ofmills adapted for the continuous rolling of the strip, means for drivingthe mills each at constant speed, and means adapted to engage the stripbetween the mills and deflect it from a straight-line path, said meansbeing effective for imposing a tension on the strip which decreases withincreasing departure. of the strip from the straight-line path.

8. Apparatus for the cold rolling of metal strip comprising a pluralityof mills adapted for the continuous rolling of the strip, tensioningmeans arranged between two successive stands adapted to engage the stripand deflect it from a straight line path between the stands and impose avarying tension thereon, and a second tensioning means arranged betweenstands at a point closer to the delivery end of the mill than thefirstmentioned tensioning device, the second tensioning device beingalso adapted to impose a varying tension on the strip but less in amountthan the first-mentioned tensioning device.

. 9. In the method of cold rolling strip metal in; a tandem mill havinga plurality of driven stands, the steps consisting in driving theseveral'stands each at constant speed, subjecting the strip tosuccessive cold reductions in the stands, maintaining the strip undertension between stands, deflecting the strip from a straight line pathin its passage between stands by the application of a deflecting force,and varying such tension by varying the deflecting force.

10. In the method of cold rolling strip metal in a tandem mill having aplurality of driven stands,

the steps consisting indriving the several stands each at constantspeed, subjecting the strip to successive cold reductions in the stands,maintaining the strip under tension between stands,

increased when a relatively hard portion of the,

strip travels between such stands.

11. In the method of cold rolling strip metal in a tandem mill having aplurality of driven stands, the steps consisting in driving the severalstands, feeding a strip therethrough and subjecting the strip tosuccessive cold reductions in the several stands, maintain g the stripunder ,tension between stands, an compensating for local irregularitiesin the strip by varying the amount of tension between two successivestands as the portion in question, is being reduced in such stands whilemaintaining the speed of such stands substantially constant.

12. Apparatus for the cold rolling of metal strip comprising spaced rollstands adapted for support. I

13. Apparatus for the cold rolling of metal strip comprising spaced rollstands adapted for the continuous rolling of the strip, means betweenthe stands for deflecting the strip from a straight line path, saidmeans being movable toward or from operative position, means for urgingthe deflecting means toward operative cluding a lever having one armoperatively connected to the deflectingmeans and'the other armoperatively connected to the urging means, a fulcrum upon which thelever is rockably mounted, a fixed support, the fulcrum being movablethereon, and means for adjusting the position of the fulcrum on thesupport.

LORENZ IVERSEN.

40 pos tion, and connections between said means in-

